1. Department of Rheumatology and Clinical Immunology, Charité-University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany
2. Department of Clinical Neurophysiology, Georg-August-University Goettingen, Robert Koch Street 40, 37075 Goettingen, Germany
3. Department of Rheumatology, Johann-Wolfgang-Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
4. HELIOS Research Center, Institute of Medical Statistics, 10117 Berlin, Germany